Age-related decrease in proteoglycan synthesis of human articular chondrocytes: The role of nonenzymatic glycation

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Abstract
Objective To examine the effect of nonenzymatic glycation of cartilage extracellular matrix on the synthetic activity of chondrocytes. Methods The proteoglycan-synthesis rate (35SO42− incorporation) and levels of advanced nonenzymatic glycation (determined by high-performance liquid chromatography measurement of pentosidine) were evaluated in human articular cartilage from 129 donors, varying in age from 25 to 88 years, and in cartilage with enhanced levels of advanced glycation end-products (AGEs) resulting from incubation with ribose. Results Cartilage showed a strong age-related increase in pentosidine levels (r = 0.97, P < 0.0005) and, concomitantly, a decrease in proteoglycan synthesis (r = −0.98, P < 0.0002). This decrease in proteoglycan synthesis correlated with the increase in pentosidine (r = −0.95, P < 0.02). Moreover, the elevation of pentosidine levels in the in vitro–ribosylated cartilage was proportional with the decrease in proteoglycan synthesis (r = −0.95, P < 0.005). Conclusion In both aged and in vitro AGE–enriched cartilage, the rate of proteoglycan synthesis was negatively correlated with the degree of glycation. This suggests that the age-related increase in cartilage AGE levels may be responsible, at least in part, for the age-related decline in the synthetic capacity of cartilage.